package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;
    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(time));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <T, ID>T queryWithPassThrough(String  keyPrefix, ID id, Class<T> type,
                                         Function<ID, T> dbFallback, Long time, TimeUnit unit){
        //1.从redis查询商铺缓存
        String key = keyPrefix+ id;
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断是否是空值
        if(json != null){
            return null;
        }
        //4.不存在，根据id查询数据库
        T t = dbFallback.apply(id);
        //5.数据库不存在，返回错误
        if(t == null){
            //将空值返回redis
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, "",  CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误
            return null;
        }
        //6.存在，写入redis
        this.set(key, t, time, unit);
        //7.返回
        return t;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <T, ID>T queryWithLogicalExpire(String keyProfix, ID id, Class<T> type, Function<ID, T> dbFallback, Long time, TimeUnit unit){
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY+ id);
        //2.判断是否存在
        if(StrUtil.isBlank(shopJson)){
            //3.存在，直接返回
            return null;
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        T t = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期，直接返回店铺信息
            return t;
        }
        //5.2.过期，需要缓存重建
        //6.重建缓存
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY+ id;
        boolean isLock = tryLock(lockKey);
        //6.2.获取锁成功，开启独立线程，实现缓存重建
        if(isLock){
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    T t1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(CACHE_SHOP_KEY+ id, t1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.3.返回过期店铺信息

        //7.返回
        return t;
    }
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

}
